3.1 - maintaining the internal environment (homeostasis) Flashcards
Organisms survive most effectively within their tolerance limits. Factors for which organisms have tolerance limits include: body temperature water availability blood glucose level carbon dioxide concentration. There are impacts on an organism when conditions fall outside its tolerance limits. Organisms detect and respond to changes in the internal and external environment. Homeostasis is the set of detections and responses that result in the internal environment of an organism remaining
What is homeostasis?
Homeostasis is the the maintenance of the internal enviorment ‘steady state’, in response to changes in both the external and internal enviornment.
What mechanisms is the steady state achieved through?
Mechanisms:
- Structural: physical features assist in tolerating changes
- Physiological: interal processes and mechanisms which detect and respond to changing conditions
- Behavioural: behaviours and actions which help organisms survive in their environment.
What are tolerance limits?
They are several variables which need to be kept within a specific range so that organisms can function and operate most efficiently; these are called tolerance limits.
Describe the body temeprature tolerance limit.
An organism’s tolerance range to temperature
36-38 degrees in humans
Control through thermoregulation:
Metabolic reactions
Physical changes
If below tolerance limits, the rate of enzyme-catalysed metabolic reactions are too slow to maintain life casuing hypothermia.
If above tolerance limits, enzymes can denature, decreasing the rate of enzyme-catalysed metabolic reactions causing hyperthermia.
What are endotherms and ectotherms?
Endotherms – generate own heat e.g. humans controling their own temperature through meabolism and physical changes.
Ectotherms – depend on external heat e.g. snakes lay in the sun so metabolic reactions can occur.
Describe the osmolarity tolerance limit.
Relates to the water/solute concentration in cells.
0.9NaCI is isotonic in human organisms.
If below tolerance limit (too dehydrated) the cell may shrink which when not enough water is avaliable, when theres too much solute affecting the folding of polypeptide and inhibting enzyme activity.
If above tolerance limit (too much water) than cells can swell and burst, the concentration of certain solute becomes too dilute reducing the rate of some life processes.
What are osmoconformers and osmoregulators?
Osmoconformers - have the same osmolarity as their enviornment e.g. jellyfish don’t have kidneys can’t regulate their osmolairty.
Osmoregulators - regulate their own osmolarity e.g. humans through which they use the excretory system (kidneys).
Describe the blood carbon dioxide concentration tolerance limit.
Carbon dioxide is removed from the body through blood(carbonic acid) controlling the rate of breathing, however the concetration of it must be kept with tolerance limits.
Typically 5-6% in humans.
If we are hypocapnia the amount of carbon in the blood is below the tolerance limit. This can lead to an increase in pH which can cause respiratory alkalosis
If were are hypercapnia the amount of carbon in our blood is above the tolerance limit and our breathing increases to try and remove the excess carbon. This can lead to an lowering in pH which can cause respiratory acidosis.
Describe blood glucose level as a tolerance limit.
Glucose is required in the blood, providing energy to our body.
For humans 75-95 mg/100mL (decilitre)
If the rate of respiration(produes glucose) is too low, a person will becomes hypoglycemic, and expereince trouble thinking as brain cells are not recieving enough energy. if untreated a person can lose consciousness and enter a coma.
If the concentraion of glucose is too high in the blood a person becomes hyperglycemic , which can lead to symptons including excessive thirst, hunger, fatigue, and/or an urge to urinate larger amounts than usual. If untreated can cause one to enter a coma and/or death.
Whats a disease through which the blood glucose level is too high?
Diabetes is a disease associated with a high level of blood glucose, usually as a reuslt of the lack of hormorne insulin or the tissues responses to insulin. *Insulin is a hormone helping your body turn food into energy and manages your blood sugar levels.
Whats the stimulus-response model?
A framework describing how indviduals respond to external stimuli:
Stimulus: a stimulus is varibale in the internal or external enviorment which is able to be detected by the organsims.
Receptorcells or tissues which detect change as a stimulus and as a result generate nerve impulses.
Transmissionrelays the infromation via nerves and/or hormones to an effector
**Effector ** a gland or muscle that brings about a response after recieving the information
**Response ** the action which occurs
Feedback positive or negative response to the initial stimulus.
What are the two types of feedback?
Negative feedback: variables trigger a counteracting repsonse to come back to the original stimulus (keeping homeostasis)
Positive feedback: ocurs when the response reinforces or brings about an increase in the inital stimulus (helping body processes.
